Electrically driven flow compressor

ABSTRACT

The invention relates to an electrically driven flow compressor comprising a drive (2, 3)—and a flow compressor and a converter (5) for electrical supply and control of the drive unit (2, 3).According to the invention, the converter (5) and the drive unit (2, 3) form an integral arrangement. Said inventive flow compressor has a reduced size, excellent electromagnetic performance and reduced production costs compared to flow drives with an external frequency converter.

[0001] The invention concerns an electrically driven flow compressor as described in the general concept of patent claim 1, specifically for use in internal combustion engines that can be charged with an exhaust turbocharger.

[0002] A turbocharger is often used in modern internal combustion engines to improve performance and reduce fuel consumption and exhaust. In particular, diesel engines are being charged today, almost exclusively diesel engines in commercial vehicles, however an increasingly important subject is also the so-called downsizing of Otto engines, i.e. a smaller engine (cubic capacity) with approximately equal engine performance. The most common process currently is charging with exhaust turbo chargers.

[0003] An exhaust turbo charger works satisfactorily upon stationary operation of the internal combustion engine. In this operating condition, the internal combustion engine generates sufficient exhaust energy to be able to drive the exhaust turbine and thereby activate the compressor of the turbocharger. In some applications, in particular for Otto engines with a spread-out rotation belt, there is a surplus of exhaust energy that would lead to an over-rev of the turbine shaft and/or excessively high charging pressure in conditions of unimpeded force on the turbine. The most common process to prevent such an occurrence is a vent valve arranged in front of the turbine that creates a bypass for the excess exhaust that is not used at the turbine. Recently, conducting devices, such as variable turbine geometry, have also been utilized. But these methods, too, use only a portion of the exhaust energy.

[0004] In non-stationary operation, i.e. when driving, accelerating, going uphill, decelerating, shifting gears, etc., which occurs primarily at small revolutions of the internal combustion engine, there is not enough exhaust energy to accelerate the exhaust turbo charger, on the one hand, and to generate sufficient charge pressure, on the other, to achieve the desired torque overload (e.g. for acceleration of the vehicle). This effect is called a “turbo hole” may only be moderated by reducing the “running shaft mass” and the interior friction of the exhaust turbocharger. This leads to ever smaller chargers with a higher number of revolutions (in excess of 200,000 l/min) and, because of the smaller flow cross-section, to an ever higher loss of flow and thereby to a poorer overall functioning. Therefore, the large-volume engine has heretofore offered only advantages.

[0005] The known solutions, the goal of which were to construct a internal combustion engine that was smaller, lighter and more cost effective, use an exhaust turbocharger with an additional electric motor to maintain rpm rate of the turbine. Such solutions have been made public, for example, in EP 0 352 064 A1, DE 35 39 782 A1 or DE 22 06450 A1. Another solution is to use an electrically driven flow compressor, in addition to an exhaust turbo charger, whose drive unit is supplied with electrical current by a separate voltage system converter. This voltage system converter is for the most part large and heavy. The current power supply of the drive unit takes place via leads that themselves isolate electromagnetic voltage (EMV) using significant screening measures.

[0006] In connection with other areas of use, electrically driven compressors are known in which the motor and the control electronics are placed in a common housing. A fluid bump of this type has been published in U.S. Pat. No. 4,511,312 A. A vacuum pump is known from U.S. Pat. No. 5,577,883 A in which the exterior pump housing is cooled by water. Cooling of the motor and or the electronics is not described. U.S. Pat. No. 5,363,674 A describes a compressor for a gaseous coolant in which the motor is arranged within the flow of the coolant so that an exchange of heat between the motor and the coolant can take place. A dedicated cooling circuit for the motor and the electronics is not described. U.S. Pat. No. 5,350,039 A also describes a compressor for a gaseous coolant in which both the motor and the electronics are in the flow of the coolant.

[0007] A dedicated cooling circuit and a common cooling element for the motor and the electronics is not provided for.

[0008] The task of the invention is to improve an electrically driven flow compressor with respect to is design size, its EMV ratio and is production costs.

[0009] This task is completed through the characteristics of patent claim 1.

[0010] According to the invention, the voltage system converter and the electric drive unit have an integral arrangement. The advantage of this arrangement is its compact design, i.e. in the compact arrangement of the drive unit and the voltage system converter. Both elements are placed close to each other in the design so as to yield advantages with respect to design size, the EMV ratio and manufacturing and service costs. The integral arrangement of the drive unit and the voltage system converter achieves significant advantages related to cooling of these components due to the fact that one and same cooling element can be used to cool the performance electronics of the voltage system converter and the drive unit. Because the drive unit has relatively high electrical power consumption, the unit utilizes a cooling circuit with a liquid coolant in a preferred execution form. The voltage system converter is preferably linked to the cooling circuit of the drive unit.

[0011] Placing the integral arrangement in a common housing is advantageous.

[0012] The stator box of the drive unit is preferably used as a cooling element for the drive unit and the performance electronics of the voltage system converter, on whose end-wall the performance electronics are arranged. By connecting the voltage system converter to the cooling circuit of the drive engine, a separate cooling of the voltage system converter is not necessary, i.e. using air or liquid. The voltage system converter can be operated in the same cooling circuit as the drive engine.

[0013] The connection leads between the drive unit and the voltage system converter are preferably kept very short—e.g. only a few millimeters—and arranged within the housing. This will cause only a very small fraction of electromagnetic radiation to be given off by these leads into the environment. This is particularly important because there is a negative effect on the environment when used in vehicles, viewed particularly in light of the great number of vehicles that leads to significant environmental burdens in areas of high density.

[0014] A preferred execution form is that the voltage system converter is linked with the drive unit via plug-in connections. A complete voltage system converter unit can be arranged and linked to the drive unit using a few fastening points. The connection of the voltage system converter with the drive unit can be a plug-in connection, whereby assembly and disassembly becomes particularly easy. Even in cases of service, the exchange of the voltage system converter can be performed easily. 

1. Electrically driven flow compressor with a drive and compressor unit and a voltage system converter (5) to supply electricity and control the drive unit whereby the voltage system converter (5) and the drive unit (2,3) have an integral arrangement that is placed in a common housing that consists of a housing part (9), a stator box (1) and a cover (4) characterized by the fact that the performance electronics (13) of the voltage system converter (5) are mounted on the housing portion on the bearing shield side of the stator box (1), the voltage system converter (5) and the drive unit (2, 3) are cooled by a common cooling element formed by the stator box (1) and the drive unit (2, 3) has a cooling circuit for a liquid coolant in which there is an empty space (7) to receive the coolant between the perimeter of the stator box (1) and the housing (9), which circulates around the stator box.
 2. Flow compressor as described in one of the preceding claims characterized by the fact that the connection leads (16) are fed between the drive unit (2, 3) and the voltage system converter (5) within the housing (1, 4, 9).
 3. Flow compressor as described in one of the preceding claims characterized by the fact that voltage system converter (5) is designed as a compact, exchangeable unit.
 4. Flow compressor as described in one of the preceding claims characterized by the fact that the voltage system converter (5) is connected via a plug-in connection with the drive unit (2, 3).
 5. Flow compressor as described in one of the preceding claims characterized by the fact that the drive unit (2, 3) is a three-phase or higher electric motor. 